Thank you for writing in, first off ensure that you are fully up to date. WordPress, Theme, and Cornerstone (Version Compatibility)
Updating Your Themes and Plugins
Then remember to clear all your caching features (plugin, server-side, CDN, and browser's cache) after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
If the issue persists, then you might need to do some editing on your Font Awesome icon codes, as of Font Awesome version 5 they split icons into multiple fonts. This can be fixed by changing instances of the
data-x-icon attribute to one of the following:
data-x-icon-b for social icons.
data-x-icon-o for outline icons.
data-x-icon-s for solid icons.
The original attribute data-x-icon will still work for solid icons as a fallback but we've updated everything for consistency.
Release Notes - Pro 2.2, X 6.2, Cornerstone 3.2
Hope it helps,